More than 2000 tots take part in a programme that teaches them water confidence and gives them essential safety skills.

The pictures were taken in pools in Cumbernauld and St Andrews and Sarah, 34, from Edinburgh, admits she had to overcome her own fear of the water to get into the pool.

She said: “It wasn’t long ago that I was terrified of the water.

“I only managed to get over it by taking my own child swimming. But now, I’m taking pictures and it’s amazing.

“Doing these photos is so much fun. Even though I’ve taken hundreds of pictures of babies, I’m constantly bowled over by how great they are in the water.

“Underwater photography is harder, and more technical, than it looks. You have a short period of time when the babies are in the pool to capture that unique shot.

“It’s stressful but worth it to see the faces of the parents when they see their little ones swimming under the surface for the first time.”

The idea of babies swimming on their own underwater is centuries old. Captain Cook observed the phenomenon during an expedition to the Pacific Islands in 1778 and, more recently, UK researchers documented the babies of indigenous Amazon families swimming in the river unaided.

Babies have a natural affinity with water – having spent months in the womb suspended in fluid.

While they lack the strength and motor skills to swim on the surface until about the age of three, they can naturally move short distances underwater from an early age.

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A German study recently found that swimming babies had more advanced motor development, social skills and intelligence than other children of the same age.

And researchers in Finland concluded that babies who could swim crawled late but walked early, having developed excellent muscle control.

More than 300,000 children under the age of two take part in swimming lessons each week in the UK – one in 10 with Water Babies, who run classes in Glasgow, Edinburgh, Stirling, Dundee and Fife.

Most babies start their lessons from six weeks old but the youngest-ever pupil was just two days old.

Among the swimming stars at the photoshoot in Cumbernauld was Holly McFarlane, one of the veterans at the tender age of eight months.

Her mother Karen said: “Nothing could have prepared me for the pleasure of seeing my daughter explore and enjoy this world of water.

“The photos are a once-in-a-lifetime opportunity and are admired by everyone.”